Alky-one gasket

ABSTRACT

A method is provided for forming a gasket for sealing opposing flange surfaces of a pipe having corrosive fluid flowing therethrough. The method comprises defining a gasket profile incorporating a serrated profile core having a flange extending radially inward therefrom. A deformable pillow extends radially inward from the serrated profile core, to define a gasket intermediate portion about the flange, and a gasket inner portion radially inward from the flange. The deformable pillow material and thickness are selected such that upon compression to a thickness no less than the core thickness, the gasket inner portion exhibits a stress level sufficient to preclude corrosive liquid flowing through the pipe from passing radially outward beyond the gasket inner portion, and the gasket intermediate portion exhibits a stress level sufficient to preclude gas and liquid flowing through the pipe from passing radially outward beyond the gasket intermediate portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.13/051,188 filed Mar. 18, 2011, which is herein incorporated in itsentirety by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND

The present invention is directed to a method for designing a gasket forfluid sealing for severe acid environments, e.g. in alkalization plants.

Sealing gaskets have been used in a variety of different applications.The construction of such gaskets is typically the function of theapplication, the environment in which the gasket will be utilized, thestress load and other factors. Where gaskets are intended to be used inseverely corrosive environments, the gasket construction will preferablyalso take into account the location of the seal(s), the need for aplurality of seals to isolate the primary seal from the corrosiveenvironment, and the need to seal the imperfections on opposing surfacesof the pipe flanges, caused by erosion from the corrosive materialfollowing through the pipe. Such imperfections are most common near theinner radius of the pipe flanges, which is closest to the corrosivematerial flowing through the pipe. Consequently, it is preferable tolocate the primary sealing element away from the inner radius of thegasket, where the adjacent surface of the flanges is less likely to bearsuch imperfections.

The particular gasket material is also a factor that is affected byapplication and environment factors. A softer, more readily conformablematerial can be useful to seal imperfections in the flange surfaces nearthe flange inner radius. However, such softer material may be lesssuitable to provide a proper seal (of sufficient stress load) to isolatethe primary seal from the corrosive material flowing through the pipe.

Further, many sealing elements operate most effectively at relativelyhigh stress levels, e.g. 20,000 to 30,000 psi or more. However, thegreater the load bearing surface of the gasket, the more distributed thegasket stress, and the lower the stress per square inch.

Accordingly, to achieve the optimum gasket design, consideration must begiven to not only the general gasket architecture, bolt load, desiredgasket stress, and environmental factors, but must also consider theneed for the different gasket components to function cooperatively in aspecific application. As such, the size, material, and functionalcharacteristics of the individual gasket elements must be carefullyengineered for cooperative interaction. Because different portions of amulti-element gasket may have different load bearing stresscharacteristics, sealing characteristics and compressibility, the gasketdesign is preferably optimized for a load specific application, allowingeach element to contribute to the functionality of the gasket, withoutdegrading the contribution of other elements.

The present invention is directed gasket design process, and amulti-zone gasket architecture, wherein each zone optimized for aspecific function by a design process that produces a gasket that, undera normal load, can produce a consistent gasket sealing stress of 20,000psi or more on the primary sealing element, which is effectively sealedfrom the corrosive environment, while also being sufficiently soft toseal imperfection in the flange surfaces.

These and other features, objects and advantages of the invention aredescribed below, in conjunction with the illustrated embodiments.

BRIEF SUMMARY

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout.

A method is provided for forming a gasket for sealing opposing flangesurfaces of a pipe having corrosive fluid flowing therethrough. Themethod comprises defining a gasket profile incorporating a serratedprofile core, the core defining a core thickness. A flange is formedextending radially inward from the serrated profile core. A deformablepillow is formed extending radially inward from the serrate profilecore, about the flange, to define a gasket intermediate portion. Thedeformable pillow further extends radially inward from the flange todefine a gasket inner portion. The deformable pillow material andthickness are selected such that upon compression to a thickness no lessthan the core thickness, the gasket inner portion exhibits a stresslevel sufficient to preclude corrosive liquid flowing through the pipefrom passing radially outward beyond the gasket inner portion, and thegasket intermediate portion exhibits a stress level sufficient topreclude gas and liquid flowing through the pipe from passing radiallyoutward beyond the gasket intermediate portion.

The serrated profile sealing element may be defined as the primarygasket seal, i.e. the gasket portion bearing the highest portion stresslevel when a specified bolt load is applied to the gasket.

The characteristics of the intermediate portion may be varied by varyingthe flange thickness to provide a desired gasket intermediate portionstress level when the gasket intermediate portion is compressed to athickness substantially corresponding to the core thickness. The gasketintermediate portion may function as a second primary seal, as it ispreferably engineered to preclude the flow liquid and gas from passingradially outward beyond the gasket intermediate seal.

The deformable pillow and pillow thickness may also be varied to providea desired gasket inner portion stress level when the gasket innerportion is compressed to a thickness substantially corresponding to thecore thickness.

The gasket core may be formed of fireproof or fireproof resistantmaterial, upon application of a designated bolt load, results in aprimary seal, which support approximately 80% of the total gasket stresslevel.

The distribution of stress levels on the gasket inner seal, and thegasket intermediate seal may be varied by regulating the variousparameters such as the deformable pillow, thickness and length, theflange thickness and length and the core thickness and length.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout.

FIG. 1 is a front perspective view of a fluid sealing gasket inaccordance with the present invention;

FIG. 2 is a top view of the gasket shown in FIG. 1;

FIG. 3 is a sectional view of the gasket;

FIG. 4 is an enlarged sectional view of a portion of the gasket shown inFIG. 3;

FIG. 5 is a cut away view of the gasket;

FIG. 6 is an enlarged sectional view of the gasket, showing differentzones, each having different stress characteristics;

FIG. 7 is a graph depicting the load characteristics of each gasketzone, for a 150 class gasket;

FIG. 8 is a graph depicting the load characteristics of each gasketzone, for a 300 class gasket;

FIG. 9 is a chart listing the gasket stress and distribution of stressfor the graphs of FIG. 7;

FIG. 10 is a chart listing the gasket stress characteristics of eachgasket zone for the graph of FIG. 8;

FIG. 11 is a graph depicting compression characteristics of the pillowmaterial used in the gasket; and

FIG. 12 is a graph depicting the compression characteristics ofdifferent gaskets.

DETAILED DESCRIPTION

The description below is given by way of example, and not limitation.Given the disclosure, one skilled in the art could devise variationsthat are within the scope and spirit of the invention disclosed herein.Further, the various features of the embodiments disclosed herein can beused alone, or in varying combinations with each other and are notintended to be limited to the specific combination described herein.Thus, the scope of the claims is not to be limited by the illustratedembodiments.

Referring to the drawings, the presently preferred embodiment of a fluidsealing gasket is illustrated therein. FIG. 1 illustrates the generalarchitecture of fluid sealing gasket 10, including an outer guide ring11, a serrated profile sealing element 13, and a deformable innerbarrier pillow 15. The inside surface of the deformable inner barrierpillow 15 defines an inner gasket surface 25. In use, the fluid sealinggasket 10 is disposed between a pair of opposing pipe flanges 12, 14, asshown in FIG. 3, and seals the connection between the flanges.

Serrated profile gaskets are used in many seals due to exceptionalsealability and reliable performance. These profiles work by having asolid serrated body, or core 17, with a flexible covering layer orfacing 21. The serrations minimize lateral movement of the facingmaterial, while the metal alloy core provides rigidity and blowoutresistance. The arrangement allows for a very high compression and anextremely tight seal along the ridges of the gasket.

The serrated profile gasket offers a safe, effective seal under the mostexacting conditions on both standard pipe work and specializedapplications. It offers excellent sealability and recoverycharacteristics, allowing seal integrity under pressure and temperaturefluctuation, temperature differentials across the flange face, flangerotation, bolt stress relaxation and creep.

The serrations concentrate load on a smaller area for a tight seal atlower stress. Under compression the sealing material fills the surfaceimperfections to form a tight connection that can withstand extremefluctuations in temperatures and pressures. The serrated profile gasketcommonly handles pressures from vacuum to Class 2500, and withstandstemperatures from cryogenics to 2000° F. (1090° C.), depending onsealing material and metal.

More detail regarding the construction of the gasket 10 is illustratedat FIGS. 4 and 5. As shown therein, the deformable barrier pillow 15defines a pillow thickness, t_(p), that is greater than the serratedprofile sealing element 13 thickness, t_(sp), or the outer guide ring 11thickness, t_(or). However, as explained in more detailed below, thepillow 15 is formed of a relatively soft, compressible material, suchthat the pillow material may be compressed to a thickness substantiallyequal to the thickness of the serrated profile sealing element 13,t_(sp).

Graphite sealing facing 13 extends over/across the serrated core 17.Upon compression, the graphite facing 13 is compressed against and fillsin the recesses defined by the core serrations 21. The flange, or innerattachment ring 19, is engaged to and extends from the serrated core 17.In the presently preferred embodiment, the serrated core 17 and flange19 are formed from a single piece of metallic alloy, such as the familyof alloys sold under the Monel trademark, but can be made of carbonsteel or other metal compatible with the application.

Monel is a trademark of special metals corporation for a service ofnickel alloys, primarily composed of nickel (up to 67%) and cooper, withsome iron and other trace elements. Monel's good resistance againstcorrosion by acids and oxygen makes Monel a good material for use inhighly corrosive environments. In the presently preferred embodimentMonel 400 is used in the construction of the serrated sealing element17.

The inner expanded PTFE barrier pillow 15 envelops the flange 19 andabuts against the core 17 and graphite facing 13.

Upon compression of the gasket 10, the inner expanded PTFE barrierpillow 15 and the graphite facing 13 are compressed to an orientationthat is substantially coplanar with the thickness of the serratedprofile sealing element 13, and defines three sealing regions along thegasket 10.

As explained further below, the particular material used form thebarrier pillow 15, and the particular thickness of the barrier 15 may beselected based upon the particular application, the bolt load applied tothe gasket as the flanges are connected, the compression and sealingcharacteristics of the pillow material, and the construction and desireddistribution of stress levels among the inner, intermediate and outersealing zones of the gasket 10.

As shown in FIGS. 4 and 6, flange 19 extends from core 17 into thepillow 15. Flange 19 defines a flange thickness, t_(f) and a flangelength, l_(f). As explained further below, the portion of pillow 15through which flange 19 extends (intermediate Zone B) exhibits differentcharacteristics in response to compression between the opposing pipeflanges 12, 14 (shown at FIG. 3). Upon compression, the stress levels onthe inner portion of pillow 15, through which flange 19 extends(intermediate Zone B), are substantially greater than the stress levelson that portion of pillow 15 between flange 19 and the gasket innersurface 20 (inner Zone A). This is because the pillow material inintermediate Zone B experiences a higher percent compression than thepillow material in inner Zone A. The higher the compression, the higherthe resulting stress level.

As shown in the embodiment illustrated at FIGS. 3 and 4, the fluidsealing gasket 10 defines a gasket width, of 1.1525 inches. The outerguide ring 11 extends approximately 30% of the gasket width. Theserrated profile core 17 extends approximately 38% of the gasket width.The flange 19 extends approximately 32% of the gasket width.Consequently, in accordance with the present invention the main sealingelement of the gasket, i.e. the core, extends over less than half of thegasket area. The size and location of the serrated core mitigatesbuckling problems and breaking associated with the conventionalspiral-wound gaskets that contain Teflon inner rings, and enhances theability of the gasket to compensate for relaxation that may occur.

In the same embodiment the exposed portion of the outer guide ringextends approximately 0.3437 inches. The unexposed portion of the outerguide ring extends approximately 0.0625 inches into the serrated profilecore. The outer guide ring has a thickness that is also approximately0.0625 inches.

The serrated profile core has a length, l_(c), of approximately 0.4375inches, and a thickness, t_(c), of approximately 0.125 inches. Theserrated profile core is preferably formed of a Monel metallic alloy.The serrated profile core flexible covering layer or facing has athickness of approximately 0.020 inches and is preferably formed of APX2Graphite, i.e., a flexible graphite material. The facing extends alongthe serrated profile core 17.

The length of the flange, or inner guide ring 19 extends approximately16% of the gasket width, i.e. approximately 0.18565 inches. The flangeis preferably formed to have a width, w_(f), of approximately 0.03125inches and a thickness t_(f) of approximately 0.069 inches.

In the preferred embodiment, the flange 19 and the serrated profile core17 may be formed as from a single, uninterrupted piece of Monel alloymaterial. FIG. 5 illustrates a construction wherein the serrated profilecore and the flange are formed of a single piece of material 20. Howeverin other constructions, the flange and the serrated profile core may beseparately formed and connected.

In one preferred embodiment, the inner barrier pillow 15 preferably isformed to extend to approximately 32% of the width of the gasket, i.e.,approximately 0.3713 inches. The barrier pillow has a thickness, t_(p),of approximately 0.250 inches and defines a slot to receive the innerguide ring. The inner barrier pillow is formed preferably of expandedPTFE, which is machined and attached to the flange/serrated profilebody, by a process in which the barrier pillow is first machined andthen attached to the flange in a manner to assure that the barrierpillow resists separation or dislodging from the serrated sealingelement inner attachment ring 19. More particularly, as described inrelation to FIG. 4, a groove or slot is cut in the outer diameter of thePTFE barrier pillow ring. To do this, the barrier pillow is clampedbetween two machined metal tools that make up a clamping device thatholds the barrier pillow by its inner diameter. The metal tool clampingdevice, with the barrier pillow clamped in it, is secured in a lathe,allowing a torque to be applied. While the metal clamping device and thebarrier pillow are rotating about its center in the lathe, a sharp toolthat cuts a groove into the barrier pillow's outer surface, shown inFIG. 4 as slot 23, that is approximately the same as the flange 19.After the groove has reached the desired depth, the sharp tool is backedout of the groove. The barrier pillow, with outer diameter groove, isthen removed from the tooling. The flange 19 is then inserted within theslot formed in the barrier pillow.

FIG. 6 illustrates the separate sealing zones of a serrated profilesealing element in accordance with the present invention. As showntherein, inner Zone A and intermediate Zone B encompass differentportions of the barrier pillow. Inner Zone A defines an inner portion ofthe barrier pillow extending from the inner surface 25 of the gasket tothe inner surface 23 of the flange 19. Intermediate Zone B defines thatportion of the barrier pillow through which flange 19 extends, i.e.,from the inner surface of the flange 19 to the inner surface 27 of theserrate profile core 17. Outer Zone C encompasses the core portionextending from the core inner surface 27 to the core outer surface 29.

Described in more detail below, inner Zone A constitutes the softestportion of the serrated profile sealing element which, when compressedbetween the flanges 12, 14 (shown at FIG. 2) will seal againstimperfections 16, 18 formed on the flanges 12, 14 respectively. The goalof this inner seal is simply to fill the area between the flanges andstop the process (caustic liquids) from being able to pass outwardlythrough the gasket to intermediate Zone B. The stress is low in thisarea, so it does not consume a high percentage of gasket stress that canbe used more effectively to seal intermediate Zone B and outer Zone C.The stress load exhibited in inner Zone A is a function ofcharacteristics of the material used to form inner Zone A, including thecompressibility of the material, and the characteristic load associatedwith the compression of the inner Zone A material to a levelsubstantially coplanar with the surface of the core 17.

Intermediate Zone B exhibits a higher stress load then inner Zone A, dueto the presence of flange 19 such that the PTFE material in intermediateZone B is more highly compressed than the PTFE material in inner Zone A.In addition to the stress load characteristics of the pillow material,the stress load characteristics of intermediate Zone B are also afunction of the thickness of the flange 19. As such, the thickness ofthe inner flange may be regulated to set the desired gasket stress inthis zone. The thicker the inner flange, the thinner the pillowmaterial, causing greater compression of the pillow material resultingin higher gasket stress. In the presently preferred embodiment, theflange thickness is set at 0.069 inches, resulting in 3,620 psi gasketstress, which is above the 2,800 psi needed to establish a gas andliquid seal for the PTFE pillow material. As such, intermediate Zone Bacts as an initial primary seal.

Ideally, the pillow material, pillow dimensions, and dimensions of theflange 19 are selected such that, upon compression of intermediate ZoneB to a level substantially coplanar with the core 21, the stress loadlevel will be at a level sufficient to provide an effective seal,precluding the flow of the caustic liquids and gasses to the primaryseal, i.e. the core. The pillow material used in the presently preferredembodiment forms a liquid and gas seal at a stress level ofapproximately 2,800 psi.

The outer Zone C gasket stresses are generally even across all gasketsizes and pressure classes. In the presently preferred embodiment, theouter Zone C gasket stresses average approximately 21,000 psi, after theload on the pillow is deducted. Consequently, even if the pillow leaks,the serrated core would keep the flange connection tight.

FIG. 7 is a graph illustrating the gasket seating stress, by zone, forclass 150 gaskets of different pipe sizes. As shown, the stress in innerZone A is consistently 680 psi, the stress in intermediate Zone B isconsistently 3,600 psi, and the stress in outer Zone C varies between13,774 psi and 22,063 psi. The average outer Zone C seating stress forthis class of gaskets is 19,922 psi.

FIG. 8 is a graph illustrating the gasket seating stress, by zone, forclass 300 gaskets of different pipe sizes. As shown, the stress in innerZone A is consistently 680 psi, the stress in intermediate Zone B isconsistently 3,600 psi, and the stress in outer Zone C varies between20,609 psi and 24,405 psi. The average outer Zone C seating stress forthis class of gaskets is 22,371 psi.

FIGS. 9 and 10 are tables of data points used to prepare FIGS. 7 and 8,and also show the total stud stress applied to the gaskets, the amountof the stud stress delivered to each zone, and the percentage of thetotal stud stress on each zone. It is shown that only a small part ofthe stud load is required to generate the gasket stresses in inner ZoneA and intermediate Zone B, while the largest fraction of stud load isdelivered to the primary seal (outer Zone C), amounting to an average of86% for class 150 gaskets (FIG. 9), and 90% for class 300 gaskets (FIG.10).

FIG. 10 illustrates the compression characteristics of the material usedto form the pillow in one presently preferred embodiment. As showntherein, a PTFE pillow, having an initial thickness of 0.250″, exhibitsa gasket stress of 680 psi when compressed 44%. This compression issufficient to establish basic fluid sealability in inner Zone A.

FIG. 11 further demonstrates the compression needed to obtain thedesired gasket stress levels for PTFE material in intermediate Zone B.For example, a 62% compression is needed to obtain 3,600 psi gasketstress in intermediate Zone B, when the material is 0.096 inches. Thislevel of compression is obtained in intermediate Zone B both through themethod of grooving the outer diameter of the PTFE barrier pillow and bythe selected thickness of flange 19, and ensures that intermediate ZoneB has sufficient seating stress to comfortably exceed the stressrequired to seal the PTFE material against both liquids and gasses.Where higher stress levels are required to form a seal for the selectedPTFE material, the thickness of the flange 19 may be increased (or thethickness of the pillow material may be altered) to obtain higherintermediate Zone B stress levels. Ideally the architecture of theserrated profile sealing element components will be such that inner ZoneA exhibits only a relatively low stress needed to prevent liquidintrusion, intermediate Zone B exhibits only a stress level sufficientto reliably form a seal that is impervious to liquids and gasses, andthe highest stress levels occur in outer Zone C, where the primarysealing resides.

Moreover, the distribution of the available stud stress is alsodependent upon the area of each Zone that is being stressed. Forexample, the shortening of flange 19 (while maintain the same length ofpillow material) will both increase the load required to compress innerZone A and decrease the load required to compress intermediate Zone B.Consequently, by appropriate engineering of the components of gasket 10,as described herein, the appropriate loads can be further distributedbetween Zones A, B and C. Ideally the distribution of the load and theoverall load itself will remain relatively constant.

FIG. 12 provides a comparison of the compression characteristics ofALKY-ONE gasket, with the compression characteristics of a spiral woundgasket having a serrated core inner ring. As shown in FIG. 12, over arange of bolt loads, the ALKY-ONE gasket is more compressible, comes tofull compression with half the bolt load, and generates much highersealing stresses in its primary seal.

Table 1 (below) shows the calculation for determining the percentagecompression of the PTFE pillow material when the load is applied to thegasket. Once the percent compression is computed, the stress loadapplied the zone may be determined by referencing the graph depictingthe compression characteristics of the pillow material used, as shown atFIG. 10.

Row Zone A Zone B 1 Original PTFE Thickness (in) 0.250 0.250 2 Cut inPTFE (in) 0.063 3 Net PTFE Thickness (in) 0.250 0.187 [Row 1 − Row 2] 4Ultimate Compressed Thickness 0.140 0.140 5 Thickness of ID Flange (in)0.069 6 Space into which PTFE is Compressed 0.140 0.071 [Row 4 − Row 5]7 Compression of PTFE (in) 0.110 0.116 [Row 1 − Row 6] 8 % Compressionof PTFE 44.0% 62.0% [1 − (Row 6/Row 3)] 9 Gasket Stress @ Above % (psi)680 3,600

As shown at Table 1, in one presently preferred embodiment the thicknessof the barrier pillow, t_(p), was selected to be 0.25 inches. In innerZone A this material is compressed down to a thickness of 0.140 inches,a level substantially coplanar with the serrated core and core facing.In intermediate Zone B, the cut in the pillow reduces the effectivethickness of the PTFE pillow to 0.187 inches, and the added presence ofthe flange 19 requires that the pillow be compressed into a gap of only0.071 inches. The compression of the PTFE in Zones A and B are thendetermined and the percentage of compression of the PTFE may becalculated. At that point, the stress level associated with thepercentage compression can be derived from the PTFE pillow compressioncharacteristics, such as shown at FIG. 10. In the presently preferredembodiment, the resulting gasket stress level in inner Zone A is 680psi, whereas the gasket stress level in intermediate Zone B is 3,600psi. As noted above, for the particular PTFE material selected, thegasket stress level in intermediate Zone B is sufficient to form aneffective seal, precluding the flow of acids to the primary seal (i.e.,the core). As such, the gasket is effective to provide dual, independentsealing zones when constructed to the referenced dimensions. In theevent that the resulting stress levels in the gasket, e.g. atintermediate Zone B, were determined to be insufficient to form aneffective seal for the selected pillow material, the gasket constructioncould be modified to enhance the stress levels in different portions ofthe gasket. For example, the thickness of the flange could be increased,the thickness of the pillow material could be decreased, or differentpillow material could be selected.

As one of ordinary skill in the art would recognize, variousenhancements, and substitutions may be made in relation to thematerials, and dimensions used for a particular implementation, withoutdeparting from the broader scope and spirit of the present invention. Assuch, those modifications, enhancements and substitutions are intendedto be encompassed within the scope of the present invention.

What is claimed is:
 1. A method of forming a gasket for sealing opposingflange surfaces of a pipe having corrosive fluid flowing therethrough,the gasket comprising: defining a gasket profile including a serratedprofile core, the serrated profile core defining a core thickness and acore inner surface; forming a flange extending radially inward from thecore inner surface, the flange defining a flange length, a flangethickness and a flange inner surface; forming a deformable pillow aboutthe flange, extending radially inward from the core inner surface,inward beyond the flange, to define a gasket inner surface; and thegasket defining an outer, high stress, fire resistant sealing zone aboutthe serrated profile core, an intermediate stress gas/liquid sealingzone between the core inner surface and the flange inner surface, and aninner, low stress liquid sealing zone between the flange inner surfaceand the gasket inner surface.
 2. The method recited in claim 1 whereineach sealing zone is formed to have a characteristic sealing stresslevel that is progressively higher from the inner sealing zone to theouter sealing zone.
 3. The method as recited in claim 2 wherein thedeformable pillow material is selected to be sufficiently deformable toseal imperfections in the opposing pipe flanges adjacent to the innersealing zone.
 4. The method as recited in claim 2 wherein when a definedbolt load is applied to the gasket the deformable pillow in the innersealing zone is compressible to a minimum inner zone stress level toprevent corrosive liquid flowing the pipe from reaching the intermediatesealing zone.
 5. The method as recited in claim 4 wherein when thedefined bolt load is applied to the gasket the deformable pillow in theintermediate sealing zone is compressible to a minimum intermediate zonestress level to prevent corrosive liquid and gas flowing through thepipe from reaching the outer sealing zone.
 6. The method as recited inclaim 5 wherein when the defined bolt load is applied to the gasket theserrated profile core exhibits a stress that is equal or greater than aminimum gasket stress level.
 7. The method as recited in claim 6 whereinthe deformable pillow defines a pillow thickness and a pillow material.8. The method as recited in the claim 4 furthering comprising the stepof selecting the pillow material and the pillow thickness to provide adesired minimum inner zone stress level when the deformable pillowmaterial in the inner zone is compressed to a thickness to no less thanthe core thickness.
 9. The method as recited in the claim 5 furtheringcomprising the step of selecting the flange thickness to provide adesired minimum intermediate zone stress level when the intermediatezone is compressed to a thickness to no less than the core thickness.10. The method as recited in claim 9 furthering comprising the step ofregulating the flange thickness such that the minimum intermediate zoneminimum stress level is no more than 21% of the gasket stress level. 11.A method of forming a gasket for sealing between opposing flangesurfaces of a pipe having a corrosive fluid flowing therethrough, themethod comprising: defining a gasket profile incorporating a serratedprofile core, the serrated profile core defining a core thickness;forming a flange extending radially inward from the serrated profilecore; forming a deformable pillow extending radially inward from theserrated profile core, about the flange, to define a gasket intermediateportion, the deformable pillow further extending radially inward fromthe flange to a gasket inner surface, to define a gasket inner portion;selecting a deformable pillow material and a deformable pillow thicknesssuch upon compression of the gasket to a thickness no less than the corethickness, the gasket inner portion exhibits a stress level sufficientto preclude corrosive liquid flowing through the pipe from passingradially outward beyond the gasket inner portion, and the gasketintermediate portion exhibits a stress level sufficient to preclude gasand liquid flowing through the pipe from passing radially outward beyondthe gasket intermediate portion.
 12. The method as recited in claim 11further comprising the step of regulating the radial length of theflange and the deformable pillow thickness such that upon application ofa designated bolt load to the gasket, the serrated profile core exhibitsa stress level that is equal to or greater than a minimum gasket stresslevel.
 13. A method of designing a sealing gasket for use between twoconnecting flanges of a pipe, the gasket defining a primary seal, anintermediate seal and an inner seal method comprising: selecting a pipediameter and a bolt load; selecting a minimum gasket primary seal stresslevel; selecting a thickness of the primary seal; forming a flangeextending radially inward from the primary seal, the flange beingenveloped by a deformable pillow material to define the gasketintermediate, the deformable pillow material extending radially inwardfrom the flange to a gasket inner surface to define a gasketintermediate seal; selecting a gasket inner seal minimum stress levelthat is sufficient to preclude liquid from passing through the innerseal; selecting a gasket intermediate seal minimum stress level that issufficient to preclude gas and liquid from passing through theintermediate seal; selecting a material for the gasket inner seal; andregulating a thickness of the inner seal to produce the gasket innerseal minimum stress level when the inner seal is compressed to athickness substantially equal to the primary seal thickness.
 14. Themethod as recited in claim 13 further comprising the step of regulatinga thickness of the flange to regulate the stress level of the gasketintermediate seal, through which the flange extends.
 15. The method asrecited in claim 14 wherein the step of regulating the thickness of theflange comprises increasing the thickness of the flange to increase theminimum stress level on the gasket intermediate seal.
 16. The method asrecited in claim 15 further comprising the step of regulating thethickness of the flange to produce the gasket intermediate seal stresslevel when the intermediate seal is compressed to a thicknesssubstantially equal to the gasket primary seal thickness.
 17. The methodas recited in claim 16 furthering comprising the step of regulating thethickness of the inner flange and of the gasket inner seal material suchthat upon application of the selected bold load to the gasket at least80% of the gasket stress is applied to the primary seal.
 18. The methodas recited in claim 16 further comprising the step of regulating thethickness of the inner flange and thickness of the gasket inner sealmaterial such that no more than 90% of the gasket stress is applied tothe primary seal.
 19. The method as recited in claim 13 wherein thesealing gasket is characterized by areas of progressively higher minimumsealing stress, extending radially outward from the gasket innersurface.
 20. The method as recited in claim 13 wherein the connectingflanges define an inner surface portions having imperfections formedtherein, and wherein the gasket inner seal is compressible to seal theimperfections.